British Airways has gained another lounge at Heathrow, and Star Alliance lost one, following BA take-over of BMI's superb Great British Lounge at London Heathrow's Terminal 1.

A highly-regarded haven in T1, the Great British Lounge was previously open to business class passengers and high-status frequent flyers of Star Alliance airlines – including Air New Zealand, Singapore Airlines and of course Lufthansa, which owned BMI until the airline was sold to BA parent International Airlines Group earlier this year.

As of Friday June 1, that's all changed.

Star Alliance will lose access to the Great British Lounge, with BA taking over and rebranding the facility as the "International Lounge", Australian Business Traveller learned on a stopover at the lounge this week.

(We also snapped the new signage, as seen below).

But beware: BA's International Lounge is not always open to Qantas frequent flyers or members of other oneworld alliances such as Cathay Pacific's Marco Polo Club.

Who gets in, and who stays out

The hidden gotcha? You have to be heading out of Terminal 1 on a flight number carrying a BA prefix, not the BD-prefix which signifies BMI.

Staff at the International Lounge's service desk told Australian Business Traveller that because BMI isn't technically considered a oneworld airline -- it's rated as a 'non-member affiliate' of BA, in the same way as Qantas' low-cost offshoot Jetstar -- travellers waving a Qantas Frequent Flyer card won't have lounge access if they're on a flight carrying BMI's BD prefix.

Lofty status won't cut any ice -- even if you're a Qantas Platinum, Macro Polo Club Diamond or enjoy similar Emerald-grade status with other oneworld airlines.

According to BA/BMI staff at the lounge desk, the only frequent flyer membership which can you into T1's International Lounge for a BD flight is that of British Airways or BMI.

That's despite the oneworld ovals on the lounge's signage which signify that emerald and sapphire frequent flyers are allowed in.

Spot those oneworld entry circles at the bottom there?

Thankfully, a change is coming

BA took over several BMI flights immediately after acquiring BMI, which is why some flights out of T1 carry the BA prefix -- and those are the ones for which oneworld Emeralds and Sapphires can enjoy lounge access before the flight.

More BMI flights will be 'converted' to BA flights as time goes on, because BA intends to absorb BMI into its core operations instead of keeping it as a subsidiary airline.

"As British Airways gradually takes over the selling of BMI routes, the code is changing to BA" a British Airways spokesperson told Australian Business Traveller. "The flight schedule for these flights, including time, date and terminal, will remain the same. British Airways plans to operate BMI's flight schedule for the (northern) summer."

The best lounge in Heathrow Terminal 1

Call it the Great British Lounge or the International Lounge, by any name it's considered the best lounge in Heathrow's Terminal 1.

Here's a quick tour... and, for once, the glitzy PR photos really do live up to their promise.

The Lobby is ideally furnished for waiting for a colleague before heading deeper into the lounge.

The chic dining room puts many business class lounges to shame.

Fancy a quick kip? The Slumber area has comfortable chaise longues where you can get some rest. Our favourite spot for privacy (and power point access) is the furthest one on the right.

The Study has PC workstations and heaps of space for your laptop.

The viewing area all the way at the far end of the lounge (next to the slumber zone) is excellent for putting your feet up too, although it's often quite busy.

But the most impressive part is the excellent provision of multiple power points by each seat, even the comfy chairs.

It's superb to see airlines realising that many business travellers want to sit down somewhere comfortable with a drink and recharge their gadgets while catching up on things with their laptop.

To get to the International Lounge, head to the far left once you're through T1 security – if you find yourself in a rather industrial set of corridors and escalators that sometimes don't seem to lead to anywhere, you're on the right track!

For the very latest news and reviews, follow Australian Business Traveller on Twitter: we're @AusBT.

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About John Walton

Aviation journalist and travel columnist John took his first long-haul flight when he was eight weeks old and hasn't looked back since. Well, except when facing rearwards in business class.